1. Field of the Invention
The present invention relates to a microwave absorber with a microwave-absorbing material, a protective housing surrounding this, and a waveguide leading into the protective housing, through which waveguide the microwaves to be absorbed can be conducted to the absorbing material.
2. Description of the Prior Art
In the operation of high-frequency high-power generators in the microwave region (e.g. gyrotrons) reflection-free loads are necessary for the absorption of the radiation energy, on the one hand in order to optimize the operational parameters with respect to wave form and power, and on the other hand in order to be able to measure the power.
Up to now there have been used for this purpose water loads with water as absorber and cooling medium: see, e.g., U.S. Pat. No. 4,593,259. With increasing frequency the depth of penetration of the electromagnetic waves continuously falls off, so that in the case of millimeter waves at last only surface absorption occurs. At high power this can lead to formation of bubbles and to boiling of the water. This results in a strong reflection of the power, whereby under certain circumstances the generator or the load or both can be damaged. Therefore, especially for optimization of the operational parameters of the generator, one must work with relatively large water throughput (e.g. 500 l/min), in order to carry away any bubbles which may arise in the stream. In most cases, however, this is expensive and impractical.